PROCESS FOR PREPARING TOLUENEDIISOCYANATE, SPECIAL MIXTURES OF TOLUENE DIAMINE AND WATER AS WELL AS THEIR USE FOR PREPARING TOLUENEDIISOCYANATE

摘要

The present invention relates to a process for preparing toluene diisocyanate by nitration of toluene to dinitrotoluene, hydrogenation of the dinitrotoluene optionally in the presence of solvents or diluents to obtain a raw toluene diamine solution and reaction water, further by treating the obtained raw toluene diamine solution to a dry toluene diamine followed up with treatment of the toluene diamine with phosgene to give toluene diisocyanate. The invented preparation process is characterized in that distillation treatment of the raw toluene diamine solution to anhydrous toluene is interrupted at the first processing station where water content in the reaction mixture ranges within 1 to 40 percent by weight, preferably 2 to 10 percent by weight and optionally after complete or partial separation of the solvents or diluents used, and so obtained mixture is transported in liquid phase and at a temperature less than or equal to 95 degC to another processing station where distillation drying of the toluene diamine is finished. After optional treatment of the dry toluene diamine in other processing stages, the toluene diamine is brought into reaction with phosgene to give toluene diisocyanate.